Venkvelaga, it is not my intention to ridicule your well-meant response, but it's wrong - DEAD wrong. If the victim (original poster) chooses to remain with her abuser, then no amount of aromatherapy, ambient lighting, or new-age philosophy is going to prevent her eventual murder - and, from her descriptions (and, if they are even remotely accurate), she will eventually be killed by her abuser.
Suggesting that the victim attempt to create an atmosphere of tranquility is the most outrageous suggestion I've read or heard in a long, long time, online or in Real Life. It is laying the actions of the abuser squarely on her shoulders and making her responsible for his choices. To even suggest such an idea tells me that you know nothing of what abuse is, why it occurs, or who is ultimately responsible for the abuse.
DO NOT even entertain the idea of slipping someone a tranquilizer, under any circumstances. It would be easily and effectively construed as attempted murder. This is a legal fact, not a feeling. Don't even frigging think about it.
There is no excuse or reason good enough to ever remain with an abuser. Someone who has threatened murder and perpetrated the types of abuses that the original poster spoke of will, without fail, end up killing his victim - either by his own hand, or by proxy. I've over a half of century of life's experiences and I can say this with complete confidence.
I would strongly urge you to visit the following website and educate yourself about domestic violence and abuse before posting any more advice to someone who might be in crisis. Not to sound harsh, but I have to call it the way that I see it, and ignorance of the facts regarding domestic violence and abuse can be very, very dangerous.